Investors showed their enthusiasm for HP's performance by clamoring for the beleaguered stock in Friday trading, sending prices up as much as 16 percent before closing at $19.20, a gain of 12.3 percent. The one-day surge was HP's largest since 2008, Forbes writer Eric Savitz reported, and the closing price was HP's highest since August.

With Friday's advance, the world's largest PC company is the best-performing stock in the Dow so far in 2013, however, as investors who want to be invested in a U.S. company in that sector are likely to soon lose the second-largest such firm, Dell, which is preparing to go private.

Analysts on Friday cheered HP's ability to succeed in a challenging environment that has forced its biggest rival to try to leave the public markets, but took pains to remind investors that the issues within the PC industry are not going anywhere.

At least eight major analysts raised their price targets -- the price at which an analyst believes it is best to sell a stock for maximum return -- by an average of $4.19 Friday, Reuters reported.

"Although the fundamentals remain mixed, the substantial improvement in free cash flow reduces the likelihood of significant downside to the stock," UBS analyst Steve Milunovich wrote in a note that included an upgrade from "Sell" to "Neutral" for the stock and an price target increase from $12 to $19. While noting the pressure of the declining industry, Milunovich wrote that "the likelihood of the bottom falling out appears diminished."

"While we think HP is being plagued by technology shifts and competitive pressure, we think CEO Meg Whitman is making good strides on stabilizing the business," S&P Capital IQ analyst Angelo Zino wrote; he maintained a "Hold" rating on the stock.

Other analysts were not as impressed with HP's performance. "The challenges across HP's portfolio and massive downsizing initiatives during this critical transition period in the IT market will leave HP less relevant over the next 12-18 months. As such, we remain sellers of HP," Topeka Capital's Brian White wrote in maintaining his "Sell" rating and $12 price target.

Einhorn won an injunction to keep Apple from asking shareholders to limit its ability to issue preferred stock, which Einhorn would like it to do. "Proposal No. 2" would force shareholders to vote on any issuance of preferred stocks, while Einhorn would like that to be a company decision, and he has asked Apple to make that move and give the preferred shares a richer dividend of 4 percent.

The legal issue is the way Apple has grouped together the proposals it will offer at its annual meeting, scheduled for Feb. 27. The proposal at issue is bundled with two other, unrelated issues, and shareholders would only be able to issue a "Yes" or "No" vote on the entire package instead of the separate proposals. Einhorn, whose Greenlight Capital fund owns 1.3 million shares of Apple after boosting its stake by about 20 percent at the end of 2012, would like to vote for the other two proposals, but not the preferred stock change.

The judge in the case on Friday said Einhorn and another investor who has joined the case "are likely to succeed on the merits and face irreparable harm if the vote on Proposal No. 2 is permitted to proceed." Judge Richard Sullivan also wrote, "Given the language and purpose of the rules, it is plain to the Court that Proposal No. 2 impermissibly bundles 'separate matters' for shareholder consideration."

He issued the preliminary injunction blocking the vote ahead of deciding the actual case, but the injunction and judge's statement seem to indicate Einhorn is likely to succeed permanently.

Apple, which has said it is not entirely opposed to pushing some of its large cash hoard back to shareholders, saw its stock price increase 1.1 percent to $450.81 Friday, its first positive move of the week.

Tech stocks recovered, with the Nasdaq advancing 1 percent and the SV150 index of Silicon Valley's largest tech companies gaining 1.3 percent. Sunnyvale Wi-Fi company Aruba had an even larger post-earnings bounce than Hewlett-Packard, as the company's stock gained 22.1 percent to close at $25.40 after trouncing analyst expectations. Aruba's rivals also profited, with newly public Ruckus advancing 7.4 percent and Meru gaining 5.2 percent; both of those companies are also based in Sunnyvale.

San Francisco social-gaming company Zynga increased 7.8 percent to $3.19 after Nevada officially legalized online poker in a plan that could allow residents of other states to play poker for real money online. Zynga has applied for a license to operate real-money online poker games in the state.

And the widely watched Standard & Poor's 500 index: Up 13.18, or 0.88 percent, to 1,515.6

Check in weekday afternoons for the 60-Second Business Break, a summary of news from Mercury News staff writers, The Associated Press, Bloomberg News and other wire services. Contact Jeremy C. Owens at 408-920-5876; follow him at Twitter.com/mercbizbreak.